The influence of track irregularities on the running behavior of high-speed trains

Abstract

Irregularities in railway tracks influence the running behavior of trains; large irregularities can result in poor ride comfort and in some cases derailment. Thus, it is important that the relationship between track irregularities and the running behavior of trains is identified and criteria for track irregularities are adequately established. However, the questions of how track irregularities affect the vehicle responses that determine running safety and ride comfort and how the wavelength and amplitude of each track irregularity influence the vehicle responses are barely addressed in the literature. This paper reports the results of computer simulation studies that were performed to investigate the influence of the longitudinal level, alignment and cross level of track irregularities on the running behavior of the 300 km/h KTX (Korea Train Express) train. A straight track was assumed in the calculations to ensure a focus on the effect of track irregularities. Track irregularities with various wavelengths and amplitudes were modeled using the VAMPIRE program; a vehicle dynamics modeling package that is widely utilized to study railway environments. Simulations on the effects of derailment coefficients, lateral loads, bogie acceleration and body acceleration created by track irregularities were performed to evaluate how the track irregularities affect the safety and ride comfort of the KTX. The results of the simulations indicate that track alignment has a significant impact on running safety whereas longitudinal level does not have any significant impacts.

A contribution for integrated analysis of railway track performance at transition zones and other discontinuities

“…For example, defects in the range D1 influence not only the resonance phenomena in sprung masses, but also semi-sprung masses of the vehicles and significantly contribute to situations of track degradation. This aspect is well documented in the literature [2][3][4]13] and was clearly demonstrated in a recent numerical parametric study carried out by the authors [30].…”

“…It would be necessary to perform additional parametric studies, similar to the numerical study by Paixão et al [30], covering different shapes of track dips for the same range of defect lengths and amplitudes, and considering other types of trains (with different axle loads and axle arrangement) and running at different speeds. Moreover, the approach does not account for the effect of alignment defects, which are known to significantly affect derailment risk [3,24,49].…”

“…While previous studies addressed the influence of the vertical stiffness on the degradation of the track [26], others did not take into account adequate representation of the variable conditions of the substructure, used a simplified numerical representation of the track substructure [14,[27][28][29]. Only a few studies seem to have focused on the relationship between the wavelength and amplitude of the defects and the track degradation or train-track interaction [3,13], though without accounting for the influence of the variable characteristics of the substructure. Questions of how changes in the physical and mechanical characteristics of the track superstructure and substructure -track discontinuities -influence the evolution of track geometry defects and how different wavelengths and amplitudes of these defects affect degradation, running safety and ride comfort are rarely addressed in the literature.…”

“…Previous studies focused mostly on the influence of track geometry defects on the vehicle dynamics, in terms of ride comfort and derailment risk [3,14,[18][19][20][21][22], while others focused on the wheel-rail interface [23][24][25]. Few studies were found in the literature addressing the impact of the train-track interaction on the degradation of the track, considering actual track geometry data.…”

“…In the long-term, this has a negative effect on the running behaviour of trains, amplifying the dynamic response of the train-track system, promoting additional track degradation, noise and vibrations, poor ride comfort and higher risk of derailment [1][2][3][4][5]. To avoid these negative aspects, railway infrastructure managers put significant effort into monitoring, maintaining and renewing railway tracks, up to specific requirements and standards [6][7][8].…”